The increase of activities of fission products and transmutation products in the primary coolant of a nuclear power plant indicates the presence of fuel rod failures. The measurement of the activity concentration of the primary coolant was able to detect fuel failures in the reactor core. Microanalytical methods for examining individual hot particles have been developed and applied to fuel failure detection under normal operation conditions as well as during the severe fuel damage that occurred in the cleaning tank incident at Unit 2 of NPP Paks in April 2003. Several faulty fuel rods can be detected simultaneously by the characterization of individual hot particles originating from the primary water. The analysis of particles originating from the damaged fuels provides information relating to the dissolution process of the fuel debris.
 P. Slavyagin, L. Lusanova and V. Miglo: “Regulation of the Fission Product Activity in the Primary Coolant and Assessment of Defective Fuel Rod Characteristics in Steady-State VVER-Type Reactor Operation”, In: Proceedings of Int. Topical Meeting on Light Water Reactor Fuel performance, Park City, Utah, April, 2000, (CD).
 J. Santucci (Ed.): Failed Fuel Action Plan Guidelines, NP-5521-SR, Special Report, 1987.
 G. Rosner: Messungen von Aktinidennukliden in Primarwasser des Kernkraftwerkes Gundremmingen, GSF-Bericht S-596, Neuherberg, 1979.
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